/Engine/Source/Runtime/SlateCore/Public/Rendering/DrawElements.h
Pushes the current widget that is painting onto the widget stack so we know what elements belong to each widget This information is used for caching later.
void PushPaintingWidget ( const [SWidget](API\Runtime\SlateCore\Widgets\SWidget) & CurrentWidget, int32 StartingLayerId, [FSlateCachedElementsHandle](API\Runtime\SlateCore\Rendering\FSlateCachedElementsHandle) & CurrentCacheHandle )